The invention relates to a projection arrangement for projecting an image onto a projection surface, said arrangement comprising a light source, a film stage, arranged following the light source, for holding a positive image recorded on a carrier medium, and projection optics for projecting a illuminated positive image. The invention further relates to a projection unit for coupling to a projector.
Such a projection arrangement is, for example, a projector for projecting a motion picture and comprises a light source, a mechanical film stage and projection optics. The light source emits a light ray bundle which illuminates positive images on a film guided transversely to the light propagation direction of the light ray bundle. The illuminated positive images are projected onto a screen by the projection optics. During operation, the film is unwound from a film reel or a film disk on one side of the film stage, guided across said film stage, and wound up on the other side of the film stage on another film reel or another film disk. The film is guided discontinuously across the film stage such that the film is moved past a picture gate on the film stage and stopped, 24 times per second, each individual image being illuminated twice. At the same time, the control signals for the theater sound system are also sampled. Such projector only allows conventional motion pictures to be projected. A simultaneous projection of additional images, which are present only as digital and/or analog data and which, in order to be projected, have to be generated first on the basis of said data, is not possible.
Such simultaneous projection of additional images is advantageous, for example, for the projection of subtitles in a foreign-language movie, because it would then no longer be required to produce individual copies of the motion picture comprising the corresponding subtitles for a certain speech area. Accordingly, the original movie could be used with corresponding subtitle files containing the data for the subtitles in the individual languages. For the projection of such subtitles, which are present only as data, projection devices may be employed which comprise light modulators for imaging, said light modulators allowing to generate the subtitles as additional images according to said data. As light modulators, for example, LCD modules or tilting mirror matrices (DMD chips) are used. If such projection arrangement is provided in addition to the projector for projecting conventional movies, this will result in a high cost of acquisition, since an entire projection arrangement needs to be acquired.
Now, the invention is intended to remedy this and to improve the aforementioned projection arrangement such that the projection arrangement is suitable for simultaneous projection of a positive image recorded on a carrier medium and of an additional image to be generated on the basis of predetermined image data. Moreover, a projection unit for coupling to a projector is to be proposed.
According to the invention, this problem is solved, in the projection arrangement of the above-mentioned type, by a control unit, a light modulator which is controllable by said control unit in order to generate an additional image on the basis of predetermined image data and which is followed by an optical device for projecting the additional image onto the projection surface, and a beam splitter arranged between the light source and the film stage, said beam splitter splitting the light from the light source into a first partial beam directed to the film stage for transilluminating the positive image and into a second partial beam, which may be directed to the light modulator.
In an advantageous embodiment of the projection arrangement according to the invention, the light incident on the beam splitter has a predetermined beam cross-section and the beam splitter is formed such that the degree of splitting between the first and second partial beam varies across the beam cross-section. For example, during the projection of subtitles as additional images, it is thus possible to illuminate the positive image with light of as great a brightness as possible, while a small area of the beam cross-section is used to impinge on the light modulator.
In an advantageous embodiment of the projection arrangement according to the invention, the beam splitter comprises a partially reflective mirror, a beam splitter block, or a deflecting element (e.g. a mirror or a prism) which is arranged partially in a beam cross-section of the light ray bundle emitted by the light source. Thus, reliable splitting of the light ray bundle is achieved.
Preferably, the projection arrangement according to the invention may be further embodied such that the beam splitter is movable into and out of the optical path between the light source and the film stage. There may further be provided a deflecting device which, when the beam splitter is moved out of the optical path between the light source and the film stage, is movable into said optical path in order to direct the light from the light source onto the light modulator. Thus, using this projection arrangement, in addition to the simultaneous projection of the additional image, this projection arrangement may also be operated such that either a illuminated positive image or an image generated by the light modulator is projected.
Preferably, the beam splitter, the light modulator and the optical device are provided as an attachable projection module. This allows the light source of a conventional projector for projecting positive images to be used also as the light source for the light modulator. Further, the conversion of an already existing, conventional projector to the projection arrangement according to the invention is easily possible, because the projection module only needs to be coupled to the conventional projector.
Particularly advantageously, the projection arrangement according to the invention may be further embodied such that a splitting device is provided which splits the light from the light source into different colors, and that the light modulator comprises several light-modulating units, each of which modulates one of said colors. This configuration allows to obtain light outputs which meet the brightness requirements of movie theaters.
In a further advantageous embodiment of the projection arrangement according to the invention, combining optics are provided which combine the light emitted by the light-modulating units to form one single light bundle and guide it to the optical device. This advantageously allows the modulated light of different colors to be imaged on the screen by means of an optical device.
Preferably, the projection arrangement according to the invention is further embodied such that the light modulator comprises an LCD modulexe2x80x94which may be in the form of a transmission or reflection modulexe2x80x94a GLV module, or a tilting mirror matrix. Thus, a high-quality image may be generated.
In a further advantageous embodiment, the projection optics and the optical device of the projection arrangement according to the invention are comprised in one single projection device. Thus, it is possible to provide a projection arrangement requiring only one projection device, which saves costs.
The projection arrangement according to the invention may advantageously be embodied such that a memory for storing data is provided. Said memory may be a digital memory, e.g. a computer hard disk, or may also be an analog memory, such as a conventional video tape. By providing such memory, the entire data for the additional images may be stored in the projection arrangement, so that there is no need for high transmission capacities of a connection with an external memory.
In another advantageous embodiment of the invention, the projection arrangement according to the invention comprises an interface for receiving data. Said interface may be, for example, a DVD drive. It may also be an interface for a computer network, such as the internet. This allows easy transmission of the data to the projection arrangement.
In a further advantageous embodiment of the invention, a display device and an image recording device are provided, said image recording device being able to record the image projected onto the projection surface and to represent it on the display device. When the image recording device records the film projected onto the projection surface and reproduces it on the display device, it is possible to control the performance from outside the auditorium. Thus, for example, failure of the projection lamp or of the auditorium lighting may be diagnosed at once.
The projection unit according to the invention for coupling to a projector, which projector comprises a light source, a film stage, arranged following said light source, for holding a positive image recorded on a carrier medium, as well as projection optics for projecting a illuminated positive image onto a projection surface, comprises a control unit, a light modulator controllable by said control unit in order to generate an additional image on the basis of predetermined image data, an optical device, arranged following the light modulator, for projecting the additional image onto a projection surface, and a beam splitter which, when the projection module is coupled to the projector, is arranged between the light source and the film stage and splits the light from the light source into a first partial beam directed to the film stage in order to illuminate the positive image and into a second partial beam which may be directed to the light modulator. This projection unit allows easy and fast retrofit of a conventional projector.